This invention relates to irrigation apparatus, and more particularly, to a mobile unit which may be transported from irrigation line to irrigation line to successively move such irrigation lines.
In U.S. Pat. No. 3,872,943 entitled "Drive Unit", assigned to the assignee of this invention, a drive unit is disclosed for rotating a wheel-supported irrigation line about its longitudinal axis to in turn transport the irrigation line across a field. While such a mover unit has proven extremely effective in operation, it is to be understood that such mover unit is designed to remain connected to an irrigation line, i.e., such mover unit is not designed to be moved from irrigation line to irrigation line to move them in succession. Rather, each irrigation line by necessity has a mover unit fixed thereto for operation therewith.
In the normal operation of such assemblies of irrigation line and mover unit, a plurality of irrigation lines, each incorporating such a mover unit, are associated with and connected to a main line, and extend from such main line on either side thereof. Under normal conditons, each irrigation line might be, for example, a quarter of a mile long, with the mover unit disposed substantially at the midpoint thereof. If such operation, each irrigation line is set in place for, for example, twelve hours, and water passes through such main line and irrigation lines to irrigate a field. The irrigation lines are then drained of water, and each irrigation line is disconnected from the main line. Each irrigation line is then transported a certain distance, i.e., for example, 60 feet by means of rotation thereof through the mover unit associated therewith, and is reconnected to the main line. It has been found that the actual time of operation of each mover unit in the transporting of such irrigation line 60 feet is but a few minutes. It has also been found that the cost of the mover unit may be approximately one third the overall cost of the combined irrigation line and mover unit. And, as set forth above, for each 12 hour operating sequence of a combined mover unit and irrigation line, such mover unit is being used for only a few minutes.
U.S. Pat. No. 3,800,820 to Trunnell discloses an irrigation pipe mover generally similar to the above-described system. That is, a mover is associated with a pipe to transport such pipe, with the mover remaining in place with such pipe even when such pipe is not being transported. Thus, it is again clear that, in the system of U.S. Pat. No. 3,800,820, each irrigation line would require such a mover for movement thereof.
In another known system, a tractor includes a rotatably drivable flange associated therewith, which may be driven by the power source of the tractor. Such tractor may be driven to the end of an irrigation line, and such flange may be bolted to the end of the irrigation line. Upon rotation of the flange and driving of the tractor, rotational torque is applied to the irrigation line to rotate it and thereby transport it over the field. Such system has proven somewhat problematical since, with a relatively long irrigation line, i.e., for example, a quarter of a mile, the opposite end of the irrigation line would not start to turn until a certain amount of twisting takes place in the line. Such opposite end of the line has been found to fall behind the end of the line associated with the tractor, and it has been found that under certain operating conditions, such opposite end of the line could fall substantially behind the end of the irrigation line associated with the tractor. In any case, it has been found that it is extremely difficult to maintain such irrigation line in a substantially straight condition.
U.S. Pat. No. 2,946,515 to Jensen and U.S. Pat. No. 3,147,746 to Jensen each disclose a system wherein a motor is positioned outwardly at the end of an irrigation line to apply rotational torque to an elongated shaft running substantially the full length of the irrigation line. It will be seen that such a system is relatively complicated, as there is no relatively direct connection between the motor and the irrigation line for efficiently applying rotational torque thereto.
Of more general interest in this area, are U.S. Pat. No. 3,561,615 to Forsberg et al., disclosing apparatus for gripping a pipe to impart axial movement thereto, U.S. Pat. No. 3,756,426 to Young, which discloses a unit capable of carrying a pipe thereon for the transport of such pipe, and U.S. Pat. No. 3,103,939 to Haugland, disclosing apparatus for pivoting a shaft about its longitudinal axis.